Refrigerating apparatus



Nov. 15, 1960 1.. J. MANN ET AL 2,959,936

REFRIGERATING APPARATUS Filed April 1, 1958 s Sheet s-Sheet 1 INVENTOR. Leonard J Mann BY Edward 0. SImmans 7' hair Attorney 54 so 44 4e Fig.

Nov. 15, 1960 L. J. MANN ETAL 2,959,936

REFRIGERATING APPARATUS Filed April 1, 1958 3 Sheets-Sheet 2 46 v INVENTOR. Fig. 7 Leonard J. Mann BY Edward 6. Simmons w A. 7' heir Af/or ey Nov. 15, 1960 J. MANN ET AL REFRIGERATING APPARATUS 3 Sheets-Sheet 3 Filed April 1. 1958 r G .m md A am I E m United States PatentO REFRIGERATING APPARATUS Leonard J. Mann and Edward C. Simmons, Dayton,

Ohio, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Apr. 1, 1958, Ser. No. 725,652

11 Claims. (Cl. 62-276) This application is a continuation-in-part of the copending applications of Leonard 1. Mann, S.N. 617,170, filed October 19, 1956, now Patent No. 2,907,180, and S.N 633,109, filed January 8, 1957, now Patent No. 2,912,834.

This invention relates to refrigerating apparatus and especially to defrosting evaporators.

When air is circulated through finned evaporators maintained below freezing temperatures, the greatest amount of frost collects adjacent to and in front of the leading edge which the inflowing air meets first. When the evaporator is heated, the frost contacting its metal surfaces melts first and the draining of the defrost water from these metal surfaces leaves a poor conducting air gap between the heated evaporator and the frost deposit especially in front of the leading edge of the evaporator. As a result, the evaporator becomes defrosted while the frost remains at and in front of the leading edge. If the defrost operation is terminated and refrigeration is resumed when the evaporator becomes defrosted, frost will remain and accumulate at and in front of the leading edge thereof. This will eventually shut off the fiow of air to the evaporator.

It is an object of this invention to provide an arrangement by which the frost at and in front of the leading edge is melted by the time the frost is melted on the remainder of the evaporator.

It is an object of this invention to arrange the entering face of the evaporator so that the frost at this face is readily disengaged and melted.

It is still another object of this invention to provide a simple, practical arrangement by which the frost in front of the leading edge rests upon a surface which will be heated during defrosting.

These and other objects are attained in the form shown in the drawings in which a duct containing a vertically finned evaporator is formed beneath the removable bottom wall of a freezing compartment. Air is drawn through the duct and the evaporator and circulated through the freezing compartment after' which it returns to the duct and the evaporator. Between the evaporator and the compartment, the air is heated by heat leakage sufficiently that its relative humidity is lowered enough that it will not deposit frost within the freezing compartment and will sublime frost which may form when the door is opened. The evaporator is normally maintained at temperatures considerably below freezing so that ice freezing may be accomplished and frozen packages maintained at a satisfactorily low temperature. Since the evaporator is at the lowest temperature of any surface in the air circuit, the frost will collect predominately on the evaporator and especially at and in front of the leading edge thereof. It is therefore necessary to periodically stop the refrigeration and heat the evaporator to defrost it.

Difliculty has been encountered in removing the frost at and adjacent to the leading edge. This difliculty is overcome by beveling the front or leading edge of the evaporator fins and by providing a conductor plate extending beneath and in front of the beveled edges so that the defrosting cycle to melt this particular accumulation of frost.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings: 7

Figure 1 is a fragmentary vertical sectional view through a household refrigerator embodying one form of my invention showing particularly the freezing compartment;

I Figure 2 is a fragmentary enlarged sectional view showing the drain-trap for the refrigerator shown in Figure 1;

Figure 3 is a fragmentary enlargedsectional view of the portion adjacent the leading edge of the evaporator showing a modified form of leading edge and conductor plate;

Figure 4 is a plan view of the drain pan shown in Figure 1;

Figure 5 is a vertical sectional view of the drain pan taken along the line 5-5 of Figure 4;

Figure 6 is a fragmentary vertical sectional view of the drain pan taken along the line 6-6 of Figure 4;

Figure 7 is a sectional view showing the duct and its contents taken along the line 77 of Figure 1; g

Figure 8 is a vertical sectional view through the'freezing compartment door shown in Figure 1 taken along the line 8-8 of Figure 9; and

Figure 9 is a top view of the inner door pan and shelves upon the door as shown in Figure 8. I

Referring now more particularly to Fig. 1, there is shown a household refrigerator cabinet including an upper food storage compartment 20 normally maintained at above-freezing tempeartures and provided withits 'own door 22. It may be cooled by either of the systems shown in, the aforementioned copending applications, S.N. 617,170 or S.N. 633,109.

Beneath the food storage compartment 20 is a freezing compartment 24 enclosed in a metal liner providing a rear wall 26, a top Wall 28 and side walls 30. The rear wall 26 has a series of seven air inlet openings 32 extending horizontally across its upper portion while each of the side walls 50 has a lower vertical series of three closely spaced elliptical openings 34 and an upper vertical series of three widely spaced elliptical openings 36 adjacent. the front edge thereof. The top wall 2 8 is provided with a series of nine air outlet openings 38 also across the front thereof. An air return duct 40 of high impact polystyrene extends across the top wall 28 and the side walls 30 covering the openings 34, 36 and 38.

It terminates at its lower end in the laterally extending projections '42 of the drainpan 44. The drain-pan 44 rests upon a molded block'of foamed polystyrene 46 which in turn rests upon the metal wall 48 extending across the top of the machine compartment 50. Both the block of insulation 46 and the drain-pin 44 are formed to provide forwardly extending drain grooves 52 and transversely extending drain grooves 54, all leading to the drain 56. v

The drain 56 includes an inner drain tube 58 of a suitable plastic or rubber having its upperedge sealed to the edges of'the drain aperture in the drain-pan 44 and an outer tube 60 surrounding the inner tube 58 and supported by a shoulder provided in the insulating block 46. The bottom of the outer tube 60 is closed by a Patented Nov. 15,

rubber or plastic cap 62 having an upwardly extending inner tube 64 extending up within the flanged thimble 66. This flanged thimble 66 has holes 68 directly above its lower flange which is located a short distance beneath the lower edge of the inner tube 58. The arrangement is such that the defrost water flowing downwardly through the inner drain tube 58 is collected on the cap 62 until the water level inside the thimble 66 rises to the top of Fig. 3 there is provided a conductor plate 92 having a turned-up front edge and a looped portion 94 extending over the front pass of the lower heater section 84 to heat the conductor plate 92 directly by the lower heater section 84 during each defrosting period. As a result, any frost accumulating in front of the leading edge of the evaporator will accumulate on the plate 92. During the defrost period, this frost will be heated rapidly by its direct conduction with the conductor plate or sheet 92 and the heater section 84 to provide quick. defrosting thereof. The bevelled edges 88 in Fig. 1 allow any frost on and projecting forward of the leading edges of the fins 80 to slide down onto the plate 92 to complete the is provided with recesses complementary to the projections 70 so as to insure its proper location upon the drain-pan 44. The evaporator 74 includes refrigerant tubing 76 formed into a horizontal serpentine shape having the long passes extending between the sidewalls 30 and having end loops 78 at the opposite ends thereof. This refrigerant tubing is provided with closely spaced vertical cross or transverse fins 80 in good heat transfer relationship therewith, These fins extend front to back. A removable bottom wall 82 rests on top of the evaporator fins 80.

To insure complete defrosting, the fins 80 are notched at nin places on their bottom edges to receive nine passes 84 of a sheathed tubular electric defrosting heater. In addition, the top edges of the fins 80 are notched at five points more deeply than the bottom edges of the fins, to receive five passes of the upper section 86 of the electric defrost heater. The two sections 84 and 86 may be continuous. As clearly shown in Fig. 6, the notches for the upper heater section 86 are sufficiently deep to space the heater section 86 entirely below the tops of the fins 80 and away from the removable bottom wall 82 to prevent direct communication of heat to this bottom wall 82. This will prevent melting of any frozen packages in the freezing compartment 24 durnig the defrost period.

It has been customary to make the front or leading edges of the evaporator 74 vertical, as shown in the aforementioned copending applications, Serial No. 617,170 and Serial No. 633,109. It was found that frost would not only collect on the leading edges of the fins of such evaporators but that the frost would extend forwardly a substantial distance into the entering passageway. The heating of the evaporator by the deforst heater would melt the frost from between the fins of the evaporator but as soon as this frost was melted, the water would be drained away. This would cause an air-gap to be formed between the front edges of the fins and the deposit of frost located in front of the front edge of the fins. This airgap prevented good conduction of the heat from the defrost heater to the accumulated frost in front of the leading edge so that this accumulated frost remained after the evaporator itself was defrosted. Unless the defrost period for the evaporator were extended long enough to remove this accumulated frost, this frost would continue to accumulate until the air circulation from the duct 40 to the front face of the evaporator was blocked. The extended defrosting was objectionable since it tended to put more heat into the freezing compartment than was absolutely necessary and might permit a rise in temperature of the packages therein,

According to this invention, instead of the front edges of the fins 80 of the evaporator being vertical, they are bevelled from top to bottom as indicated by the reference character 88 in Fig. 1 and 90 in Fig. 3. The bevels 88 and 90 are at an angle of about 45 in opposite directions. It is found that either is satisfactory. Beneath the front edges of the evaporator 74 in either Fig. lot

melting thereof during the defrost period. In the form shown in Fig. 3, the frost forming on and in advance of the leading bevelled edge 90 will fall down or slide down off this leading edge onto the conductor plate 92 and be melted thereon. This cures a very troublesome defrost problem. r r

The ducts 40 terminate in the projections 42 in the drain-pan 44, These projections 42 communicate directly with the space in front of the leading bevelled edges 88 I or 90 of the fins 80 of the evaporator 74. To, force the terminate short of the rear wall 26 to provide a discharge passage, The rear edge of the bottom wall 82 is provided with a turned-up flange 121 which receives a breaker strip 123 of plastic or rubber having a longitudinal notch receiving the flange 121. The breaker strip 123 also has a longitudinal notch on its upper edge for receiving the lower edge of a metal inlet shroud 125 having a downwardly turned flanged top portion 127 fitting into the notch 129 on the back wall 26 to form with the space behind the rear end of the evaporator an inlet passage 131. The rear wall 26 is provided with a flanged outlet opening 133 extending into the interior of the centrifugal fan 135.

This fan 135 is located in the molded discharge scroll 137 provided on the rear face of the rear wall 26 surrounding the opening 133. This scroll discharges into the discharge duct 139 also provided on the rear face of the rear wall 26 for conducting the air discharged from the wheel 135 and the scroll 137 to the inletair openings 32. Foamed polyurethane insulating plastic 141 is cast about the ducts 40, 139 and the scroll 137 as well as the side walls 30, the remainder of the rear wall 26 and the top wall 28 to provide an integral freezing compartment assembly. The blower scroll is provided with a flattened extension 143 through which the blower wheel may be inserted and withdrawn. This flanged opening normally is filled with a cylindrical shaped piece 145 of a foamed polystyrene. Fastened to this flange 143 is a mounting ring 147 provided with resilient motor supports 149 for resiliently supporting the fan motor 151. The fan motor 151 has a forwardly extending drive shaft extending through an aperture in the insulation piece 145 and connecting to the blower wheel 135 within the scroll 137. A neoprene diaphragm seal 153 extends between the motor 151, the mounting ring 147 and a clamping ring 155 which clamps the outer edges of the seal 153 to the rear outer metal wall 157 of the cabinet. The insulation 141 is provided with a notch 159 for receiving the drain tube 161 from the food compartment 20.

Between the food compartment 20 and the freezing compartment 24 there is provided a removable mullion 163 forming the bottom breaker strip of the food compartment, the top breaker strip of the freezing compartinent, and the connecting outer wall between. It containsa block of plastic insulating material 165 as well as an illuminating light 167. This mullion 163 with the plastic insulation 165 and the light 167 may be removed so that the top, rear and side walls of the freezing compartment 24 along with the integral insulation can be readily inserted and removed. The bottom wall 82 and the evaporator 74'as Well'as the shroud 125 are separately removable. 1 In the event that any water or frost should collect at thebottom of-the duct 139 or the scroll 137, there is provided an additional defrost heater portion 169 in the bottom thereof to melt and evaporate any frost and water collecting therein. This heater 169 may be connected either in series or in parallel with the heater sections 84 and 86. These defrost heaters may be connected in an electric defrosting circuit such asis shown in the aforementioned copending applications, S.N. 617,- 170 or S.N. 633,109. Also, if desired, the defrost system may be like that shown in Fig. 1 of Patent 1,913,433 issued June 13, 1933, or Fig. 2 of Patent 2,780,925 issued February 12, 1957. The defrost period is preferably terminated under control of the thermostat 170 located in the lower duct provided by the drain pan 44 on the left side of the evaporator 74.

The outlets 34 and 36 on the sidewalls are covered by vertical plastic strips '171 having horizontal slots therein to permit the flow of air. The front edges of the bottom wall 82 and the sidewalls 30 extend into the kerf at the rear edge of a molded'plastic breaker strip 173 having a notch formed at its front edge which is adapted to'fit the curled edge of the front-wall 175 of the cabinet.

The front of the freezing compartment 24 is closed by the insulated door 177. The inner face 179 of this door is provided with vertical grooves 181 for providing a circulation of cold air behind the upper and lower plastic shelves 183 and 185 which are fastened to the inner face of the door 177. For the purpose of holding articles on the lower shelf, there is provided a swinging wire bail 187 pivoted at the rear and having a bar extending across the front. This bail 187 may be lifted toa horizontal position to permit ready placing of articles on the shelf 185 and then allowed to drop by gravity to. the lower position indicated in Fig. 8 wherein it will preventarticles from toppling off the shelf 185 in the event that the door 177 is opened suddenly.

-At the side of the shelves 183 and 185 is a rack 189 having five individual shelves 191 for holding small cans 193 with'their axes horizontal. These racks 191 have turned-up outer edges and a 'deep notch 195 to permit easy gripping of the cans 193 for renewal. The notches 195 also provide improved air circulation around the cans 193 so that they are more rapidly cooled.

To assure defrosting of the area of the drain pan 44 immediately around the drain tube there is provided an inverted U-shaped conductor strip 221 (see Fig. 3) hav ing its upper connecting portion contacting bottom surface of the conductor plate 92 and the adjacent portions of the lower heater section '84. The legs of the strip 221 have outwardly extending-flanges resting upon a good heat conducting mastic 223 adhering to the adjacent upper surface of the drain pan 4-4. To hold the lower heater section 84, the conductor plate 92 and the conductor strip 221 in good heat transfer relationship with the drain pan 44-, clamps and screws 225 extend between the sides of the evaporator 74 and the drain pan 44 for clamping them together so as to clamp the conductor strip 221 in between.

When the lower heater section 84 is energized during the defrosting period, the heat will be conducted from the section 84 through the conductor plate 92 and the strip 221 and the mastic 223 to the area of the drain pan d4 around the drain 56 to permit the free escape of the defrost water from the evaporator 74 and the drain pan 44 during defrosting.

While the' embodiment of the *presentinvention as herein disclosed constitutes a preferred form, it is to he ing means in the form of tubing located generally between two parallel horizontal planesprovided with spaced parallel upright elongated fins in heat exchange relation thereto each substantially transverse to said planes and having their long edges substantially parallel to said planes, a removable heat transfer member having extensive horizontal areas in contact with the long edges of said fins in one of said planes, fan means for circulating air between said fins entering adjacent one of the short edges and leaving adjacent the opposite short edge, means for heating said evaporating means to defrost it, the upper edges of said fins nearest the entrance of the air protruding beyond the lower edges to assist in melting the frost adjacent the entrance.

2. Refrigerating apparatus including tubular evaporating means in the form of tubing located generally be-.

tween two parallel planes provided with spaced parallel upright elongated fins in heat exchange relation thereto each substantially transverse to said planes and having their long edges substantially parallel to said planes, means for circulating air between said fins entering adjacent one of the short edges and leaving adjacent the opposite short edge, means for heating said evaporating means to defrost it, the short edges of said fins nearest the entrance of the air being beveled substantially from top to bottom to assist in melting the frost adjacent the entrance, and a substantially horizontal conductor sheet extending into heat transfer relation with said heating means and across the bottoms of and in contact With extensive edge portions of said fins substantially from one edge of the evaporating means to the other adjacent said beveled edges and protruding from said beveled edges to further assist in melting the frost adjacent the entrance.

3. Refrigerating apparatus including a substantially horizontal wide duct, a tubular evaporating means in the form of'tubing extending within the duct provided with spaced parallel horizontally elongated upright fins extending substantially from the top to the bottom of'the duct and in heat exchange relation with said tubing, the top and bottom edges of thefins being notched, an electric defrost heater extending through said notches for defrosting said evaporating means, means for circulating air through said duct between said fins, the leading edges of said fins being beveled relative to the bottom edges of said fins substantially from top to bottom with the bottom edges as the protruding edges to assist in melting the frost adjacent said leading edges.

4. Refrigerating apparatus including a substantially horizontal wide duct, a tubular evaporating means in the form of tubing extending Within the duct provided with spaced parallel elongated upright fins extending substantially from top to the bottom of .the duct'and in heat exchange relation with said tubing, the top and .bottorn edges of the fins being notched, an electric defrost heater extending through said notches for defrosting said eVaPQr rating means, means for circulating air through said duct between said fins, the leading edges of said fins being beveled substantially from top to bottom to .assist in melting the frost adjacent said leading edges, and a conductor sheet extending into contact with the bottoms of the fins over the bottom of said duct and extending in heat exchange relation with a portion of said heater and also extending beyond the leading edge of the fins toward the supply of air for further assisting in the melting of the frost.

5. Refrigerating apparatus including a drip pan provided with drain grooves and a drain, an evaporating means supported on said drip pan including spacedparallel upright fins and tubing extending transversely through the fins in heat exchange relation therewith, side and top and rear walls joined together resting upon said drip pan enclosing a freezing compartment, insulation bonded to said side andtop and rear walls, a removable bottom wall resting upon the top of the fins of said evaporating means forming a duct enclosing the evaporating means, an air duct hollowed out of said insulation cornmunicating with the interior of said freezing compartment and extending from one portion of a side and top wall to the duct formed beneath the removable bottom wall adjacent the leading edge of said evaporating means, and means for circulating air from said compartment through said air duct and the duct beneath the bottom wall and the evaporating means and returning the air to another portion of the compartment.

6. Refrigerating apparatus including a drip pan provided with drain grooves and a drain, an evaporating means supported on said drip pan including spaced parallel upright fins and tubing extending transversely through the fins in heat exchange relation therewith, side and top and rear walls joined together resting upon said drip pan enclosing a freezing compartment, insulation bonded to said side and top and rear walls, a removable bottom wall resting upon the top of the fins of said evaporating means forming a duct enclosing the evaporating means, said fins having notches on their upper and lower edges, an electric defrost heater extending through said notches in heat exchange relation with said fins and said drip pan, the notches on the upper edge of said fins being deeper to space the heater away from said bottom wall.

7. Refrigerating apparatus including a drip pan provided with drain grooves and a drain, an evaporating means supported on said drip pan including spaced parallel upright fins and tubing extending transversely through the fins in heat exchange relation therewith, side and top and rear walls joined together resting uponsaid drip pan enclosing a freezing compartment, insulation bonded to said side and top and rear walls, a removable bottom wall resting upon the top of the fins of said evaporating means forming a duct enclosing the evaporating means, said fins having notches on their upper and lower edges, an electric defrost heater extending through said notches in heat exchange relation with said fins and said drip pan, the notches on the upper edge of said fins being deeper to space the heater away from said bottom wall, the leading edges of the fins being beveled substantially from top to bottom, said heater having a portion extending beneath the fins adjacent and parallel to said leading edges, and a conductor sheet protruding from beneath the leading edges of said fins and having a portion extending beneath and in contact with the bottoms of the leading edges of said fins and over and partially around in contact with said heater portion for assisting in the removal of frost adjacent the leading edges, of said fins.

8. Refrigerating apparatus including a drip pan provided with drain grooves and a drain, an evaporating means supported on said drip pan including spaced parallel upright fins and tubing extending transversely through the fins in heat exchange relation therewith, side and top and rear walls joined together resting upon said drip pan enclosing a freezing compartment, insulation bonded to said side and top and rear walls, a removable bottom wall resting upon the top of the fins of said evaporating means forming a duct enclosing the evaporating means, a fan having its inlet communicating with said duct formed between said drip pan and said bottom wall, an inlet shroud extending from said bottom wall over the inlet to said fan, and a breaker strip of poor heat conducting material sealing the space between adjacent parts of said shroud and said bottom wall 9.Refrigerating apparatus including a drip pan provided with drain grooves and a drain, an evaporating means supported on said drip pan including spaced parallel upright fins and tubing extending transversely through the fins in heat exchange relation therewith, side and top and rear walls joined together resting upon said drip pan enclosing a freezing compartment, insulation bonded to said side and top and rear walls, a removable bottom wall resting upon the top of the fins of said evaporating means forming a duct enclosing the evaporating means, a fan having its inlet communicating with said duct formed between said drip pan and said bottom wall, and a discharge duct for said fan hollowed out of said insulation and extending to said compartment.

10. Refrigerating apparatus including a drip pan provided with drain grooves and a drain, an evaporating means supported on said drip pan including spaced parallel upright fins and tubing extending transversely through the fins in heat exchange relation therewith, side and top and rear walls joined together resting upon said drip pan enclosing a freezing compartment, insulation bonded to said side and top and rear walls, a removable bottom wall resting upon the top of the fins of said evaporating means forming a duct enclosing the evaporating means, a fan having its inlet communicating with said duct formed between said drip pan and said bottom wall, and a discharge duct for said fan hollowed out of said insulation and extending to said compartment, defrost heating means for said evaporating means having a heating portion located in said discharge duct.

11. Refrigerating apparatus including a drip pan, side and top and rear insulated walls associated with said pan to form an insulated compartment, means for cooling said compartment, insulating means beneath the drip pan, pan and insulating means being provided with a drain passage having an upwardly facing shoulder, an outer tube within said drain passage supported by said shoulder and extending beneath the bottom of the drain passage, a removable cap of elastomeric material extending over and surrounding the bottom of said tube and having an integral upwardly extending inner tube open at the bottom extending upwardly in the tube, and a thimble-shaped member within said outer tube extending over said inner tube to form a water sealing trap. 

